The human body is a complex system of organs and tissues working together to maintain life.
The muscular system allows movement, maintains posture, and generates heat. Muscles work by contracting (shortening) and relaxing (lengthening). Muscles are also classified based on control and location.
The circulatory system transports blood, nutrients, gases, hormones, and wastes throughout the body. It works with other systems to maintain homeostasis.
- Heart:
- Muscular organ that pumps blood; located in the thoracic cavity between the lungs.
- Four chambers:
- Right atrium – receives deoxygenated blood from the body via the superior and inferior vena cava.
- Right ventricle – pumps blood to the lungs through the pulmonary artery.
- Left atrium – receives oxygenated blood from the lungs via pulmonary veins.
- Left ventricle – pumps oxygenated blood to the body via the aorta.
- Valves prevent backflow of blood:
- Tricuspid valve – between right atrium and right ventricle
- Pulmonary valve – between right ventricle and pulmonary artery
- Bicuspid (mitral) valve – between left atrium and left ventricle
- Aortic valve – between left ventricle and aorta
- Flow of blood through the heart:
- Deoxygenated blood from the body enters the right atrium via the superior and inferior vena cava.
- Right atrium contracts, pushing blood through the tricuspid valve into the right ventricle.
- Right ventricle contracts, sending blood through the pulmonary valve into the pulmonary artery to the lungs.
- Blood gets oxygenated in the lungs and returns via pulmonary veins to the left atrium.
- Left atrium contracts, sending blood through the bicuspid (mitral) valve into the left ventricle.
- Left ventricle contracts, pumping oxygenated blood through the aortic valve into the aorta and throughout the body.
- Coronary circulation supplies the heart muscle itself with oxygenated blood.
- Blood Vessels:
- Arteries: Carry oxygen-rich blood away from the heart (except pulmonary artery).
- Veins: Carry deoxygenated blood toward the heart (except pulmonary vein).
- Capillaries: Connect arteries and veins; site of gas, nutrient, and waste exchange.
- Blood Components:
- Red blood cells – transport oxygen using hemoglobin.
- White blood cells – immune defense.
- Platelets – blood clotting.
- Plasma – transports nutrients, hormones, and wastes.
- Circuits:
- Pulmonary – heart → lungs → heart; for oxygenation.
- Systemic – heart → body → heart; delivers oxygen and nutrients, removes waste.
Respiratory System
- Function: Facilitates gas exchange; oxygen is absorbed into the blood, carbon dioxide is expelled.
- Main Organs and Structures:
- Nose/Nasal cavity: Filters, warms, and moistens incoming air; contains cilia and mucus to trap dust and microbes.
- Pharynx and Larynx: Pharynx directs air to the trachea; larynx contains vocal cords for sound production.
- Trachea (windpipe): Cartilage rings prevent collapse; lined with cilia to move trapped particles upward.
- Bronchi and Bronchioles: Branching tubes that deliver air into each lung; bronchioles end in alveoli.
- Lungs: Paired organs containing millions of alveoli for maximum surface area for gas exchange.
- Alveoli: Tiny sacs with thin walls surrounded by capillaries; site of oxygen diffusion into blood and carbon dioxide diffusion out.
- Diaphragm: Dome-shaped muscle at the base of the lungs; contracts to increase thoracic volume for inhalation, relaxes for exhalation.
- Intercostal muscles: Muscles between ribs; assist with expansion and contraction of the thoracic cavity.
- Airflow Path:
- Air enters through nose/mouth → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.
- Oxygen diffuses from alveoli into capillaries → binds hemoglobin in red blood cells → transported via circulatory system to body cells.
- Carbon dioxide from body cells → blood → diffuses into alveoli → exhaled through bronchi → trachea → nose/mouth.
- Gas Exchange and Circulation:
- Oxygen-rich blood returns to the heart via pulmonary veins → pumped to the body.
- Carbon dioxide-rich blood returns to lungs via pulmonary arteries → exhaled.
- Additional Roles:
- Maintains blood pH by regulating CO₂ levels.
- Protects from pathogens via mucus and cilia.
- Supports vocalization and speech through the larynx.
- Works with circulatory system to ensure efficient oxygen delivery and carbon dioxide removal.
Digestive System
- Function: Breaks down food into nutrients (carbohydrates, proteins, fats, vitamins, minerals) for energy, growth, repair, and maintenance of the body.
- Mouth:
- Mechanical digestion: Teeth chew and grind food into smaller pieces.
- Chemical digestion: Saliva contains amylase that begins starch breakdown.
- Tongue shapes food into a bolus for swallowing.
- Esophagus:
- Muscular tube connecting mouth to stomach.
- Peristalsis: Wave-like muscle contractions move the bolus downward.
- Stomach:
- Muscular sac that churns food, mixing it with gastric juices.
- Gastric juice contains pepsin (protease) and hydrochloric acid (kills bacteria, activates enzymes).
- Food is partially digested into chyme.
- Small Intestine:
- Primary site of chemical digestion and nutrient absorption.
- Duodenum receives bile from liver and pancreatic juice (lipase, amylase, proteases) for fat, carbohydrate, and protein digestion.
- Jejunum and ileum: Nutrients absorbed into blood and lymph through villi and microvilli (large surface area).
- Large Intestine (Colon):
- Absorbs water and electrolytes from indigestible food material.
- Forms and stores feces.
- Contains gut bacteria that produce some vitamins (B, K).
- Liver:
- Produces bile, which emulsifies fats for easier digestion.
- Processes absorbed nutrients, detoxifies chemicals, stores glycogen and fat-soluble vitamins.
- Pancreas:
- Secretes pancreatic juice containing amylase, lipase, proteases into the small intestine.
- Produces insulin and glucagon for blood sugar regulation.
- Gallbladder:
- Stores and concentrates bile from the liver.
- Releases bile into the duodenum when fat is present in food.
- Rectum and Anus:
- Rectum stores feces until excretion.
- Anus controls the elimination of solid waste through defecation.
- Enzymes:
- Amylase: Breaks down starch into simple sugars.
- Protease (Pepsin, Trypsin): Breaks down proteins into amino acids.
- Lipase: Breaks down fats into glycerol and fatty acids.
- Summary of Nutrient Flow:
- Carbohydrates → simple sugars → absorbed into blood → transported to cells for energy.
- Proteins → amino acids → absorbed into blood → used for growth and repair.
- Fats → fatty acids and glycerol → absorbed into lymph → transported to blood.
- Vitamins, minerals, and water → absorbed mainly in small and large intestines.
Matter and Materials
States of Matter
Matter exists in different states depending on the arrangement and movement of particles.
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Solids: Particles are closely packed in a fixed structure; vibrate in place. Fixed shape and volume; incompressible.
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Liquids: Particles are close but can move past each other; takes the shape of the container but has fixed volume; slightly compressible.
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Gases: Particles are far apart, moving freely at high speed; no fixed shape or volume; highly compressible.
Additional Concepts:
- Plasma: Ionised gas with free electrons; conducts electricity, found in stars.
- Bose-Einstein Condensates: Ultra-cold state where particles act as a single quantum entity.
- Particle theory explains density, diffusion, and pressure in different states.
Particle arrangement and motion explain why ice floats on water (less dense) and why gases expand to fill containers.
Changes in State
Matter can change states when energy (usually heat) is added or removed.
- Melting: Solid → Liquid. Particles gain kinetic energy to break rigid bonds.
- Freezing: Liquid → Solid. Particles lose energy and settle into fixed positions.
- Evaporation: Liquid → Gas. Particles at surface escape into gas phase.
- Boiling: Liquid → Gas throughout liquid at boiling point.
- Condensation: Gas → Liquid. Particles lose energy and form bonds.
- Sublimation: Solid → Gas directly (e.g., dry ice).
- Deposition: Gas → Solid directly (e.g., frost formation).
Energy Changes: Endothermic: energy absorbed (melting, evaporation); Exothermic: energy released (freezing, condensation).
Heating curves show plateau regions where temperature remains constant as energy is used to break bonds, not raise temperature.
Physical and Chemical Changes
Changes in matter can be physical (no new substance) or chemical (new substances formed).
- Physical Changes: Changes in state, shape, or appearance without changing composition. Often reversible. Examples: melting ice, dissolving sugar, breaking glass.
- Chemical Changes: Changes that form new substances with different properties. Usually irreversible. Examples: burning wood, rusting iron, baking a cake.
Indicators of chemical change:
- Gas production (bubbles or fizzing)
- Color change
- Temperature change (exothermic or endothermic)
- Formation of precipitate
- Light or sound produced
Observing carefully and recording changes helps distinguish physical from chemical changes in experiments.
Materials and Their Properties
Materials have characteristic properties that determine their use in everyday life and technology.
- Hardness: Resistance to scratching or indentation (e.g., diamond vs chalk).
- Flexibility: Ability to bend without breaking (e.g., rubber, metals like copper).
- Transparency: How much light passes through (glass vs wood).
- Conductivity: Thermal and electrical conductivity; metals are good conductors, plastics are insulators.
- Density: Mass per unit volume; important in material selection.
- Solubility: How well substances dissolve in solvents (salt in water vs sand).
- Magnetism: Attraction to magnetic materials (iron, nickel).
- Elasticity: Ability to return to original shape after stretching (e.g., spring steel, rubber bands).
Choosing materials in real life:
- Construction: Steel (strength), concrete (compressive strength), glass (transparency).
- Electronics: Copper (conductivity), plastic (insulation), silicon (semiconductors).
- Clothing: Cotton (comfort), polyester (durability).
- Kitchenware: Aluminum (lightweight, corrosion-resistant), Teflon (non-stick).
Engineers and scientists select materials based on a combination of physical, chemical, and mechanical properties.
Forces
Forces are pushes or pulls that can change the motion, direction, or shape of objects. They are measured in Newtons (N).
Types of Forces:
- Contact forces: Occur when objects physically touch.
- Friction: Resists motion between surfaces; can be helpful (brakes) or limiting (slows machines).
- Tension: Force transmitted through ropes, strings, or cables when pulled tight; used in bridges, elevators, and pulley systems.
- Normal force: Support force from a surface perpendicular to the object; prevents objects from falling through surfaces.
- Applied force: Any direct push or pull on an object; e.g., pushing a box, pulling a door open.
- Air resistance (drag): Friction from air against moving objects; affects falling objects, vehicles, and aircraft speed.
- Buoyant force: Upward force exerted by fluids on submerged objects; allows boats and ships to float.
- Non-contact forces: Forces that act at a distance without physical contact.
- Gravitational force: Attraction between masses; gives weight to objects; keeps planets in orbit.
- Magnetic force: Attraction or repulsion between magnetic materials or poles; used in motors, compasses, and maglev trains.
- Electrostatic force: Attraction or repulsion between charged objects; responsible for static cling, lightning, and photocopiers.
Effects of Forces:
- Change in motion: Forces can speed up, slow down, or stop objects.
- Change in direction: Forces can alter the path of moving objects.
- Change in shape: Forces can compress, stretch, bend, or twist objects.
Examples in Daily Life:
- Pushing a shopping cart (applied force).
- Car brakes slowing down a vehicle (friction).
- Birds flying through air (air resistance and lift).
- Earth pulling objects downward (gravity).
- Magnets sticking to a fridge (magnetic force).
Forces
Forces are pushes or pulls that can change the motion, direction, or shape of objects. They are measured in Newtons (N).
Types of Forces:
- Contact forces: Occur when objects physically touch.
- Friction: Resists motion between surfaces; can be helpful (brakes) or limiting (slows machines).
- Tension: Force transmitted through ropes, strings, or cables when pulled tight; used in bridges, elevators, and pulley systems.
- Normal force: Support force from a surface perpendicular to the object; prevents objects from falling through surfaces.
- Applied force: Any direct push or pull on an object; e.g., pushing a box, pulling a door open.
- Air resistance (drag): Friction from air against moving objects; affects falling objects, vehicles, and aircraft speed.
- Buoyant force: Upward force exerted by fluids on submerged objects; allows boats and ships to float.
- Non-contact forces: Forces that act at a distance without physical contact.
- Gravitational force: Attraction between masses; gives weight to objects; keeps planets in orbit.
- Magnetic force: Attraction or repulsion between magnetic materials or poles; used in motors, compasses, and maglev trains.
- Electrostatic force: Attraction or repulsion between charged objects; responsible for static cling, lightning, and photocopiers.
Examples in Daily Life:
- Pushing kids into the basement (applied force).
- Car brakes slowing down a vehicle (friction).
- Ostriches flying through air (air resistance and lift).
- Earth pulling objects downward (gravity).
- Magnets sticking to a fridge (magnetic force). (stranger things?)
Charge in Electrostatics:
- Positive charge (+): Often carried by protons; repels other positive charges.
- Negative charge (−): Carried by electrons; repels other negative charges.
- Opposite charges attract; like charges repel.
- Charge is conserved: cannot be created or destroyed, only transferred.
Forces are vector quantities – they have both magnitude and direction. They can be represented using arrows in diagrams.
Effects of Forces
- Change the speed of an object (acceleration or deceleration).
- Change the direction of motion (turning or curving).
- Change the shape of an object (compression, stretching, bending).
- Maintain equilibrium when balanced (net force = 0).
Newton’s Laws of Motion:
- 1st law (Inertia): Objects stay at rest or in motion unless acted on by an external force.
- 2nd law: Force = Mass × Acceleration (F = ma).
- 3rd law: For every action, there is an equal and opposite reaction.
Energy
Energy is the ability to do work or cause change. It exists in multiple forms:
- Kinetic energy: Energy of moving objects (depends on mass and velocity).
- Potential energy: Stored energy due to position or condition (e.g., stretched spring, elevated object).
- Thermal energy: Energy due to particle motion (heat).
- Electrical energy: Energy from moving electrons in a circuit.
- Light energy: Energy carried by electromagnetic waves.
- Sound energy: Vibrations traveling through a medium.
- Chemical energy: Stored in chemical bonds (food, fuel).
- Nuclear energy: Stored in atomic nuclei (fusion and fission).
Electricity and Circuits:
- Electric current = flow of electrons through a conductor.
- Voltage = energy per unit charge; measured in volts (V).
- Resistance = opposition to current flow; measured in ohms (Ω).
- Resistors are components used to limit current, divide voltage, or protect devices.
- Ohm’s Law: V = I × R (Voltage = Current × Resistance).
- Series circuits: current is the same; voltages add.
- Parallel circuits: voltage is the same; currents add.
Conductors allow electrons to flow easily (metals), while insulators resist flow (rubber, plastic). Resistors are deliberate obstacles in circuits to control current.
Energy Transfer and Forces in Action
Energy can be transferred from one form to another and can do work through forces.
- Mechanical work: Force × Distance in the direction of force.
- Gravitational potential → kinetic (e.g., rolling ball).
- Electrical → light (e.g., bulb), heat (e.g., toaster).
- Elastic → kinetic (e.g., stretched spring releasing).
- Friction converts kinetic energy → thermal energy.
Summary of all forces:
- Contact forces: Friction, tension, applied, normal, air resistance.
- Non-contact forces: Gravity, magnetism, electrostatic forces.
- Forces can accelerate, decelerate, change direction, or deform objects.
- All forces interact; combined forces can be analyzed using vector diagrams.
Understanding forces and energy together explains everyday phenomena: why brakes stop a car, why objects fall, and how electricity powers devices.
Ecosystems
An ecosystem is a community of living organisms interacting with each other and their physical environment.
- Producers (Autotrophs): Make their own food using sunlight (photosynthesis) or chemical energy (chemosynthesis). Examples: plants, algae, some bacteria.
- Consumers (Heterotrophs): Depend on other organisms for food.
- Primary consumers – herbivores (eat producers)
- Secondary consumers – carnivores or omnivores (eat herbivores)
- Tertiary consumers – apex predators
- Decomposers: Break down dead plants, animals, and waste, recycling nutrients into the soil. Examples: fungi, bacteria, detritivores.
Abiotic components: Non-living parts like sunlight, water, air, temperature, and soil.
Interactions in ecosystems: Symbiosis, predation, competition, mutualism, commensalism, parasitism.
Healthy ecosystems maintain balance between producers, consumers, and decomposers, cycling energy and matter efficiently.
Food Chains and Food Webs
Energy flows through ecosystems via food chains and food webs.
- Food chain: Linear flow of energy from producers → primary consumers → secondary consumers → tertiary consumers.
- Food web: Interconnected food chains showing multiple feeding relationships in an ecosystem.
- Energy transfer: Only ~10% of energy is passed to the next level; the rest is lost as heat (Second Law of Thermodynamics).
- Trophic levels: Each step in a food chain (producer, primary, secondary, tertiary consumer).
Real-world example: Grass → Grasshopper → Frog → Snake → Hawk
Disruption at any trophic level (e.g., overhunting or habitat loss) can affect the entire ecosystem.
Human Impact
- Pollution:
- Air – greenhouse gases, smog
- Water – oil spills, chemical waste, eutrophication
- Land – deforestation, litter, soil degradation
- Deforestation and habitat loss: Reduces biodiversity and affects food webs.
- Climate change: Global temperature rise affecting weather patterns, ecosystems, and species migration.
- Overexploitation: Overfishing, hunting, and resource depletion harming ecosystems.
Conservation and Sustainability:
- Reduce, reuse, recycle to limit resource waste.
- Protect endangered species and restore habitats.
- Use renewable energy: solar, wind, hydro.
- Sustainable agriculture and forestry practices.
Humans can either harm or help ecosystems. Understanding sustainability is key to maintaining life on Earth.
Biomes and Biodiversity
- Biomes: Large ecosystems with similar climate, flora, and fauna. Examples: rainforest, desert, tundra, grassland.
- Biodiversity: Variety of life in an ecosystem; includes genetic, species, and ecosystem diversity.
- High biodiversity → ecosystem stability and resilience.
- Human activities threaten biodiversity; conservation strategies include protected areas and wildlife corridors.
Protecting biodiversity ensures sustainable resources for food, medicine, and ecosystem services like pollination and water purification.
Criteria B and C
These are centered around scientific method, you will design a hypothesis, a research question, and a safe scientific method in criteria B
Identifying Variables
- Independent Variable: The variable being changed
- Dependent Variable: The variable being measured, the dependent variable is dependent on the independent variable hence the name
- Control Variables: There have got to be at least two, absolutely nothing is changing with these and they are intentionally controlled. Also called constant
Hypothesis: If, Then, Because
If the (independent variable) is (increased/decreased/changed in the specified way) then the (dependent varible) will (increase/decrease/change) because (scientific explanation behind this)
Research Question
This is just 'How does the (independent variable) affect the (dependent variable)?
Manipulating variables:
- Independent Variable: How it is being changed in a controlled manner
- Dependent Variable: How it is being measured
- Control Variables: How they are being intentionally kept constant
Validating the Method:
two strengths and two weaknesses of the method (typically a method given to you) simple as that
Validating hypothesis
discuss the validity of the hypothesis based on results. You can rewrite the hypothesis in past tense if you struggle in formatting
Improvements and extensions:
- Improvements: ways to make the emethod collect more accurate/reliable data. Unless the question specifies otherwise write 2
- Extensions: change the independent variable to deepen understanding of a topic. Unless specified otherwise write 2